Experimental chronic lingual candidosis induced in streptozotocin diabetic rats

Characteristics of lingual papillae in diabetic rats

Diabetes mellitus (DM) is a metabolic disorder resulting with many different complications including soft tissue abnormalities in the oral cavity such as periodontitis and salivary and taste dysfunction. Previous studies also reported fungal and bacterial infections in oral cavity in these patients. This study aims to represent three dimentional morphologic ultrastructural changes of the diabetic rat tongue via scanning electron microscopy. Twenty-four (24) adult male Spraque-Dawley rats, (weight ranging between 200-250g) included in the study were randomly assigned into two groups: control rats were injected with intraperitoneally saline alone, experimental diabetes group received streptozotocin (STZ) (80mg/kg) administrated intraperitoneally. On month four, by the end of experimental period, all animals of each group were anesthetised. All tongues were dissected totally, postfixed in 2% osmium tetroxide and then dried by critical point drying before SEM analysis. Finally, superficial epithelial configurations of the lingual papillae in experimental diabetic rats were examined by scanning electron microscopy. Diabetes mellitus caused thickness, hyperceratosis and different epithelial changes, We observed yeast-like structures and bacterial colonisations on the papillar and epithelial structure of the tongue. The morphological atrophic changes of lingual mucosa and the median rhomboid glossitis (which is primary finding of candidal infection) are characteristic observations on the lingual mucosa of the streptozotocin treated rats.

Antimicrobial agent, tetracycline, enhanced upper alimentary tract Candida albicans infection and its related mucosal proliferation in alloxan-induced diabetic rats

Alloxan-induced diabetic rats showed proliferative changes in the forestomach, accompanied by chronic inflammation, and one lesion progress to squamous cell carcinoma (SCC) without distant metastasis. The authors demonstrated that these lesions might be caused by Candida albicans infection. Antimicrobial therapy, particularly tetracycline treatment, has been blamed for a reduction in the number of competing bacterial organisms, which is frequently mentioned as a cause of candidiasis. The objective of this study is to ascertain whether or not tetracycline treatment can accelerate early-onset of C. albicans infection and the proliferative changes in this diabetic model. Alloxan-induced diabetic rats were given chlorinated water (AL group) and tetracycline solution (0.1% during week 1 and 0.01% thereafter) as drinking water (AT group). They were sacrificed after 25 weeks of drinking the treated water. The infection rate with C. albicans in the AT group was significantly higher than in the AL group. The incidence and severity of the squamous cell hyperplasia were enhanced in the AT group compared to the AL group. The proliferative lesions were consistently accompanied by inflammation and C. albicans infection in both groups. SCC was detected in one case in the AT group. These findings demonstrate that tetracycline induces C. albicans infection and enhances forestomach proliferative lesions in alloxan-induced diabetic rats.

Effects of the antifungal agent itraconazole on proliferative changes of the forestomach mucosa in alloxan-induced diabetic rats

Alloxan-induced diabetic rats frequently exhibit proliferative lesions of squamous hyperplasia accompanied by chronic inflammation and Candida albicans infection in the forestomach, and some lesions progress to squamous cell carcinoma (SCC). Candida infection causes not only hyperplastic changes with inflammation but might also lead to SCC in human oral mucosa. Thus, the present study was conducted to examine the effects of the antifungal agent itraconazole (ITCZ) on proliferative and inflammatory changes of the forestomach in alloxan-induced diabetic WBN/Kob rats. Diabetes was induced by alloxan at fifteen weeks of age. Rats were allocated to three groups at forty-five weeks of age and were given ITCZ by gavage 0 (vehicle control), 5, and 10 mg/kg/day for four weeks, and they were sacrificed at the sixty-fifth week of age. Mucosal hyperplastic changes were consistently accompanied by inflammation and Candida infections in the 0 mg/kg group. These lesions were reduced by ITCZ (0 mg/kg; 100%, 5 mg/kg; 53.5%, 10 mg/kg; 61.5%). Squamous cell carcinoma was detected in three rats from the 0 mg/kg, but only one rat from the 10 mg/kg dose groups in this study. Itraconazole reduced the degree of mucosal hyperplasia, inflammatory changes, and Candida infection. Therefore, C. albicans infection was an important factor in pathogenesis of mucosal proliferation and inflammation.

Clinical spectrum of oral candidosis and its role in HIV-infected patients

Oral candidosis is a very frequent diseased state occurring mainly together with severe underlying disease. Clinical manifestation is variable. One can distinguish between oral thrush, denture stomatitis, angular cheilitis, leukoplakia and midline glossitis. Nowadays oral candidosis is also important in connection with HIV-infection. Here the clinical spectrum does not seem to be totally different. Apart from oral thrush (or pseudomembraneous type) a chronic atrophic type, a chronic hyperplastic type, papillary hyperplasia and angular cheilitis are distinguished. Oral candidosis is the most frequent opportunistic infection in HIV-infected patients. Frequency of overt disease is linked to the T4/T8 ratio. In patients with AIDS-related complex oral candidosis seems to be indicative of rapid progression. Candida albicans is the prevailing microorganism. There is, however, a change of biotypes during the course of HIV-infection. There seems to be a selection of certain phenotypes as can be judged from the increasing resistance to 5-fluorocytosine.

Prevention of proliferative changes of forestomach mucosa by blood glucose control with insulin in alloxan-induced diabetic rats

Diabetes mellitus is one of the risk factors for carcinogenesis. Recently we reported that alloxan induces squamous cell carcinoma (SCC) with coincidental inflammation, bacteria/fungal infections, and a severe diabetic condition. The present study was conducted to examine the effects of blood glucose control with insulin on the proliferative changes of the forestomach in alloxan-induced diabetic rats. Male 15-week-old WBN/Kob rats were divided into a control group of non-treated rats with naturally occurring diabetes after 40 weeks of age (non-treated group), alloxan-induced diabetic rats (AL group), and alloxan-induced diabetic rats given insulin implant treatment (AL + In group). The animals were sacrificed at 90 weeks of age for histopathologic examination. The blood glucose and urinary glucose level of the AL + In group fluctuated variously from high to normal levels compared with a constantly high level of AL (for 75 weeks) as well as in the non-treated group (for 50 weeks). The mucosal hyperplasia in the forestomach developed in 88.2% of the AL group and 37.5% of the non-treated group, but in only 10.0% of the AL + In group. SCC was only detected in 23.5% of the AL group. Hyperplastic changes were constantly accompanied by inflammation and fungal/bacterial infections in the AL and non-treated groups, whereas inflammation and fungal infection were completely suppressed in the AL + In group. These findings demonstrate that blood glucose control suppressed neoplastic changes in alloxan-induced diabetic rats. We postulate that inflammation together with bacterial/fungal infections under prolonged severe diabetic conditions play a pivotal role in carcinogenesis.

Diabetes mellitus as a contributory factor in oral candidosis

It has been reported that poor glycaemic control predisposes to oral candidal infection in diabetic patients. For instance, the carriage of Candida species and the density of candidal growth in the oral cavity is frequently claimed to be increased in patients with diabetes mellitus. However, the validity of these observations remains controversial. Hence, we review and discuss here the clinical data in the literature on the relationship between diabetes and oral candidal carriage and infection, and possible mechanisms associated with its pathogenicity.

Experimental oral candidiasis in animal models

Oral candidiasis is as much the final outcome of the vulnerability of the host as of the virulence of the invading organism. We review here the extensive literature on animal experiments mainly appertaining to the host predisposing factors that initiate and perpetuate these infections. The monkey, rat, and mouse are the choice models for investigating oral candidiasis, but comparisons between the same or different models appear difficult, because of variables such as the study design, the number of animals used, their diet, the differences in Candida strains, and the duration of the studies. These variables notwithstanding, the following could be concluded. (i) The primate model is ideal for investigating Candida-associated denture stomatitis since both erythematous and pseudomembranous lesions have been produced in monkeys with prosthetic plates; they are, however, expensive and difficult to obtain and maintain. (ii) The rat model (both Sprague-Dawley and Wistar) is well proven for observing chronic oral candidal colonization and infection, due to the ease of breeding and handling and their ready availability. (iii) Mice are similar, but in addition there are well characterized variants simulating immunologic and genetic abnormalities (e.g., athymic, euthymic, murine-acquired immune deficiency syndrome, and severe combined immunodeficient models) and hence are used for short-term studies relating the host immune response and oral candidiasis. Nonetheless, an ideal, relatively inexpensive model representative of the human oral environment in ecological and microbiological terms is yet to be described. Until such a model is developed, researchers should pay attention to standardization of the experimental protocols described here to obtain broadly comparable and meaningful data.

Animal models of oral candidiasis. A review

Candida albicans is the most common fungal infection of the human oral mucosa, yet much remains to be understood with respect to the pathogenesis of the disease. Numerous difficulties are inherent in designing studies that use human beings as subjects. The use of various animal species in experimental contexts has helped to provide insight with respect to this condition. A variety of manipulations of the system can be performed, including altering the host immune response, the mucosal environment, or the systemic environment. In addition, organism-related factors can be examined in a more controlled setting. The information obtained from such studies could not be obtained in an in vitro situation.

Clinical, histologic and scanning electron microscopic study of the development of chronic candidiasis of the rat tongue

In order to examine the development of the chronic candidal lesion of the dorsal rat tongue, 210 rats were given a single oral inoculum of Candida albicans on Day 0 and were sequentially killed over a 20-wk period. Dorsal tongue changes were evaluated using clinical photographs, histologic sections and scanning electron microscopy (SEM). Clinically evident lesions became apparent at 2 wk post-inoculation, and inflammatory changes of the underlying connective tissue were observed by 3 wk post-inoculation. SEM showed a gradient of destruction of the dorsal tongue papillae at the periphery of the candidal lesions. Hyphae were seen infrequently on the lesional surface by SEM, a finding which correlated with the light microscopy.